For the purpose of constituting an adverse possession by a person claiming title not founded upon a written instrument, or judgment, or decree, land shall be deemed to have been possessed and occupied in the following cases only:

1. (1) Where it has been protected by a substantial inclosure; or
2. (2) Where it has been usually cultivated or improved.

Source: SDC 1939 & Supp 1960, § 33.0224.